In the art of bedding for rest and relaxation of human beings, it has long been a practice to provide bed structures with means to vibrate, shake or otherwise impart motion into and throughout the bed structures which will induce relaxation and/or release the tension of persons lying on the beds.
Mechanical means such as motor-driven crank and lever type means and other motor driven eccentric drive means have been provided to physically move desired portions of beds in efforts to impart comforting cyclical motion into the beds. Such means have proven impractical since the sound level generated thereby is oftentimes excessive; they are costly to make; they require the construction of special bed structures to accommodate them; and they are subject to breaking down or to cause the breaking down and failure of the bed structures with which they are related.
The most common form of means for imparting restful and/or relaxing motion in bed structures has been the provision and use of electro-mechanical vibrators or transducer units; which units are related to the bed structures in such a manner that the motion generated by the units is transmitted in and through the beds in an effective manner.
The principal difficulty and/or shortcoming found in the use of electro-mechanical transducer units in bed structures resides in the fact that such units provided by the prior art are designed and constructed to operate at one unalterable, uncontrolled and unspecified frequency. In most instances, the units are fabricated without a consideration given to their resonant frequency and are likely to have a frequency between 40 and 60 Hz.
In practice, the most common and available electro-magnetic transducer units used in the furniture and/or bedding art are U-shaped, strap metal springs in the nature of tuning forks. One leg or arm of the spring in this form of unit is used as a mounting plate or pad to secure the unit to a related structure to be shaken. The other leg or arm of the tuning fork-like spring is the movable part of the structure and has an induction coil fixed to its free end portion to occur in limited working clearance with and above said one leg or arm. The working clearance afforded is the required gap clearance for the resulting electro magnetic device and is such that it limits the amplitude of the vibrating motion and resulting power output of the device.
The above noted common class of transducer is so designed that it is excessively large for its power output, is of undesirable shape or poorly proportioned for use in water beds and many other environments and is notably inefficient with respect to power in and power out.
In light of the foregoing, it has been determined that the need exists for an electro-magnetic transducer unit for use in connection with water beds and the like which is comparable in size with the above noted common class of transducer but which is more efficient and puts out far greater power relative to power put in; and which is such that its natural frequency can be effectively adjusted and set in synchronism with its related power supply.